Documentation for actix multipart (#3344)

example for actix-multipart readme & crate docs

Co-authored-by: Rob Ede <robjtede@icloud.com>

actix-multipart/src/lib.rs

@@ -1,4 +1,39 @@
 //! Multipart form support for Actix Web.
+//! # Examples
+//! ```no_run
+//! use actix_web::{post, App, HttpServer, Responder};
+//!
+//! use actix_multipart::form::{json::Json as MPJson, tempfile::TempFile, MultipartForm};
+//! use serde::Deserialize;
+//!
+//! #[derive(Debug, Deserialize)]
+//! struct Metadata {
+//!     name: String,
+//! }
+//!
+//! #[derive(Debug, MultipartForm)]
+//! struct UploadForm {
+//!     #[multipart(limit = "100MB")]
+//!     file: TempFile,
+//!     json: MPJson<Metadata>,
+//! }
+//!
+//! #[post("/videos")]
+//! pub async fn post_video(MultipartForm(form): MultipartForm<UploadForm>) -> impl Responder {
+//!     format!(
+//!         "Uploaded file {}, with size: {}",
+//!         form.json.name, form.file.size
+//!     )
+//! }
+//!
+//! #[actix_web::main]
+//! async fn main() -> std::io::Result<()> {
+//!     HttpServer::new(move || App::new().service(post_video))
+//!         .bind(("127.0.0.1", 8080))?
+//!         .run()
+//!         .await
+//! }
+//! ```
 
 #![deny(rust_2018_idioms, nonstandard_style)]
 #![warn(future_incompatible)]